5 default "/lib/modules/$(shell,uname -r)/.config"
6 default "/etc/kernel-config"
7 default "/boot/config-$(shell,uname -r)"
9 default "arch/$(ARCH)/defconfig"
12 def_bool $(success,$(CC) --version | head -n 1 | grep -q gcc)
16 default $(shell,$(srctree)/scripts/gcc-version.sh -p $(CC) | sed 's/^0*//') if CC_IS_GCC
20 def_bool $(success,$(CC) --version | head -n 1 | grep -q clang)
24 default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
33 config BUILDTIME_EXTABLE_SORT
36 config THREAD_INFO_IN_TASK
39 Select this to move thread_info off the stack into task_struct. To
40 make this work, an arch will need to remove all thread_info fields
41 except flags and fix any runtime bugs.
43 One subtle change that will be needed is to use try_get_task_stack()
44 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
53 depends on BROKEN || !SMP
56 config INIT_ENV_ARG_LIMIT
61 Maximum of each of the number of arguments and environment
62 variables passed to init from the kernel command line.
65 bool "Compile also drivers which will not load"
69 Some drivers can be compiled on a different platform than they are
70 intended to be run on. Despite they cannot be loaded there (or even
71 when they load they cannot be used due to missing HW support),
72 developers still, opposing to distributors, might want to build such
73 drivers to compile-test them.
75 If you are a developer and want to build everything available, say Y
76 here. If you are a user/distributor, say N here to exclude useless
77 drivers to be distributed.
80 string "Local version - append to kernel release"
82 Append an extra string to the end of your kernel version.
83 This will show up when you type uname, for example.
84 The string you set here will be appended after the contents of
85 any files with a filename matching localversion* in your
86 object and source tree, in that order. Your total string can
87 be a maximum of 64 characters.
89 config LOCALVERSION_AUTO
90 bool "Automatically append version information to the version string"
92 depends on !COMPILE_TEST
94 This will try to automatically determine if the current tree is a
95 release tree by looking for git tags that belong to the current
98 A string of the format -gxxxxxxxx will be added to the localversion
99 if a git-based tree is found. The string generated by this will be
100 appended after any matching localversion* files, and after the value
101 set in CONFIG_LOCALVERSION.
103 (The actual string used here is the first eight characters produced
104 by running the command:
106 $ git rev-parse --verify HEAD
108 which is done within the script "scripts/setlocalversion".)
111 string "Build ID Salt"
114 The build ID is used to link binaries and their debug info. Setting
115 this option will use the value in the calculation of the build id.
116 This is mostly useful for distributions which want to ensure the
117 build is unique between builds. It's safe to leave the default.
119 config HAVE_KERNEL_GZIP
122 config HAVE_KERNEL_BZIP2
125 config HAVE_KERNEL_LZMA
128 config HAVE_KERNEL_XZ
131 config HAVE_KERNEL_LZO
134 config HAVE_KERNEL_LZ4
137 config HAVE_KERNEL_UNCOMPRESSED
141 prompt "Kernel compression mode"
143 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED
145 The linux kernel is a kind of self-extracting executable.
146 Several compression algorithms are available, which differ
147 in efficiency, compression and decompression speed.
148 Compression speed is only relevant when building a kernel.
149 Decompression speed is relevant at each boot.
151 If you have any problems with bzip2 or lzma compressed
152 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
153 version of this functionality (bzip2 only), for 2.4, was
154 supplied by Christian Ludwig)
156 High compression options are mostly useful for users, who
157 are low on disk space (embedded systems), but for whom ram
160 If in doubt, select 'gzip'
164 depends on HAVE_KERNEL_GZIP
166 The old and tried gzip compression. It provides a good balance
167 between compression ratio and decompression speed.
171 depends on HAVE_KERNEL_BZIP2
173 Its compression ratio and speed is intermediate.
174 Decompression speed is slowest among the choices. The kernel
175 size is about 10% smaller with bzip2, in comparison to gzip.
176 Bzip2 uses a large amount of memory. For modern kernels you
177 will need at least 8MB RAM or more for booting.
181 depends on HAVE_KERNEL_LZMA
183 This compression algorithm's ratio is best. Decompression speed
184 is between gzip and bzip2. Compression is slowest.
185 The kernel size is about 33% smaller with LZMA in comparison to gzip.
189 depends on HAVE_KERNEL_XZ
191 XZ uses the LZMA2 algorithm and instruction set specific
192 BCJ filters which can improve compression ratio of executable
193 code. The size of the kernel is about 30% smaller with XZ in
194 comparison to gzip. On architectures for which there is a BCJ
195 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
196 will create a few percent smaller kernel than plain LZMA.
198 The speed is about the same as with LZMA: The decompression
199 speed of XZ is better than that of bzip2 but worse than gzip
200 and LZO. Compression is slow.
204 depends on HAVE_KERNEL_LZO
206 Its compression ratio is the poorest among the choices. The kernel
207 size is about 10% bigger than gzip; however its speed
208 (both compression and decompression) is the fastest.
212 depends on HAVE_KERNEL_LZ4
214 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
215 A preliminary version of LZ4 de/compression tool is available at
216 <https://code.google.com/p/lz4/>.
218 Its compression ratio is worse than LZO. The size of the kernel
219 is about 8% bigger than LZO. But the decompression speed is
222 config KERNEL_UNCOMPRESSED
224 depends on HAVE_KERNEL_UNCOMPRESSED
226 Produce uncompressed kernel image. This option is usually not what
227 you want. It is useful for debugging the kernel in slow simulation
228 environments, where decompressing and moving the kernel is awfully
229 slow. This option allows early boot code to skip the decompressor
230 and jump right at uncompressed kernel image.
234 config DEFAULT_HOSTNAME
235 string "Default hostname"
238 This option determines the default system hostname before userspace
239 calls sethostname(2). The kernel traditionally uses "(none)" here,
240 but you may wish to use a different default here to make a minimal
241 system more usable with less configuration.
244 # For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can
245 # add proper SWAP support to them, in which case this can be remove.
251 bool "Support for paging of anonymous memory (swap)"
252 depends on MMU && BLOCK && !ARCH_NO_SWAP
255 This option allows you to choose whether you want to have support
256 for so called swap devices or swap files in your kernel that are
257 used to provide more virtual memory than the actual RAM present
258 in your computer. If unsure say Y.
263 Inter Process Communication is a suite of library functions and
264 system calls which let processes (running programs) synchronize and
265 exchange information. It is generally considered to be a good thing,
266 and some programs won't run unless you say Y here. In particular, if
267 you want to run the DOS emulator dosemu under Linux (read the
268 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
269 you'll need to say Y here.
271 You can find documentation about IPC with "info ipc" and also in
272 section 6.4 of the Linux Programmer's Guide, available from
273 <http://www.tldp.org/guides.html>.
275 config SYSVIPC_SYSCTL
282 bool "POSIX Message Queues"
285 POSIX variant of message queues is a part of IPC. In POSIX message
286 queues every message has a priority which decides about succession
287 of receiving it by a process. If you want to compile and run
288 programs written e.g. for Solaris with use of its POSIX message
289 queues (functions mq_*) say Y here.
291 POSIX message queues are visible as a filesystem called 'mqueue'
292 and can be mounted somewhere if you want to do filesystem
293 operations on message queues.
297 config POSIX_MQUEUE_SYSCTL
299 depends on POSIX_MQUEUE
303 config CROSS_MEMORY_ATTACH
304 bool "Enable process_vm_readv/writev syscalls"
308 Enabling this option adds the system calls process_vm_readv and
309 process_vm_writev which allow a process with the correct privileges
310 to directly read from or write to another process' address space.
311 See the man page for more details.
314 bool "uselib syscall"
315 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
317 This option enables the uselib syscall, a system call used in the
318 dynamic linker from libc5 and earlier. glibc does not use this
319 system call. If you intend to run programs built on libc5 or
320 earlier, you may need to enable this syscall. Current systems
321 running glibc can safely disable this.
324 bool "Auditing support"
327 Enable auditing infrastructure that can be used with another
328 kernel subsystem, such as SELinux (which requires this for
329 logging of avc messages output). System call auditing is included
330 on architectures which support it.
332 config HAVE_ARCH_AUDITSYSCALL
337 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
341 depends on AUDITSYSCALL
346 depends on AUDITSYSCALL
349 source "kernel/irq/Kconfig"
350 source "kernel/time/Kconfig"
351 source "kernel/Kconfig.preempt"
353 menu "CPU/Task time and stats accounting"
355 config VIRT_CPU_ACCOUNTING
359 prompt "Cputime accounting"
360 default TICK_CPU_ACCOUNTING if !PPC64
361 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
363 # Kind of a stub config for the pure tick based cputime accounting
364 config TICK_CPU_ACCOUNTING
365 bool "Simple tick based cputime accounting"
366 depends on !S390 && !NO_HZ_FULL
368 This is the basic tick based cputime accounting that maintains
369 statistics about user, system and idle time spent on per jiffies
374 config VIRT_CPU_ACCOUNTING_NATIVE
375 bool "Deterministic task and CPU time accounting"
376 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
377 select VIRT_CPU_ACCOUNTING
379 Select this option to enable more accurate task and CPU time
380 accounting. This is done by reading a CPU counter on each
381 kernel entry and exit and on transitions within the kernel
382 between system, softirq and hardirq state, so there is a
383 small performance impact. In the case of s390 or IBM POWER > 5,
384 this also enables accounting of stolen time on logically-partitioned
387 config VIRT_CPU_ACCOUNTING_GEN
388 bool "Full dynticks CPU time accounting"
389 depends on HAVE_CONTEXT_TRACKING
390 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
391 select VIRT_CPU_ACCOUNTING
392 select CONTEXT_TRACKING
394 Select this option to enable task and CPU time accounting on full
395 dynticks systems. This accounting is implemented by watching every
396 kernel-user boundaries using the context tracking subsystem.
397 The accounting is thus performed at the expense of some significant
400 For now this is only useful if you are working on the full
401 dynticks subsystem development.
407 config IRQ_TIME_ACCOUNTING
408 bool "Fine granularity task level IRQ time accounting"
409 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
411 Select this option to enable fine granularity task irq time
412 accounting. This is done by reading a timestamp on each
413 transitions between softirq and hardirq state, so there can be a
414 small performance impact.
416 If in doubt, say N here.
418 config HAVE_SCHED_AVG_IRQ
420 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
423 config BSD_PROCESS_ACCT
424 bool "BSD Process Accounting"
427 If you say Y here, a user level program will be able to instruct the
428 kernel (via a special system call) to write process accounting
429 information to a file: whenever a process exits, information about
430 that process will be appended to the file by the kernel. The
431 information includes things such as creation time, owning user,
432 command name, memory usage, controlling terminal etc. (the complete
433 list is in the struct acct in <file:include/linux/acct.h>). It is
434 up to the user level program to do useful things with this
435 information. This is generally a good idea, so say Y.
437 config BSD_PROCESS_ACCT_V3
438 bool "BSD Process Accounting version 3 file format"
439 depends on BSD_PROCESS_ACCT
442 If you say Y here, the process accounting information is written
443 in a new file format that also logs the process IDs of each
444 process and its parent. Note that this file format is incompatible
445 with previous v0/v1/v2 file formats, so you will need updated tools
446 for processing it. A preliminary version of these tools is available
447 at <http://www.gnu.org/software/acct/>.
450 bool "Export task/process statistics through netlink"
455 Export selected statistics for tasks/processes through the
456 generic netlink interface. Unlike BSD process accounting, the
457 statistics are available during the lifetime of tasks/processes as
458 responses to commands. Like BSD accounting, they are sent to user
463 config TASK_DELAY_ACCT
464 bool "Enable per-task delay accounting"
468 Collect information on time spent by a task waiting for system
469 resources like cpu, synchronous block I/O completion and swapping
470 in pages. Such statistics can help in setting a task's priorities
471 relative to other tasks for cpu, io, rss limits etc.
476 bool "Enable extended accounting over taskstats"
479 Collect extended task accounting data and send the data
480 to userland for processing over the taskstats interface.
484 config TASK_IO_ACCOUNTING
485 bool "Enable per-task storage I/O accounting"
486 depends on TASK_XACCT
488 Collect information on the number of bytes of storage I/O which this
493 endmenu # "CPU/Task time and stats accounting"
497 depends on SMP || COMPILE_TEST
500 Make sure that CPUs running critical tasks are not disturbed by
501 any source of "noise" such as unbound workqueues, timers, kthreads...
502 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
503 the "isolcpus=" boot parameter.
507 source "kernel/rcu/Kconfig"
514 tristate "Kernel .config support"
517 This option enables the complete Linux kernel ".config" file
518 contents to be saved in the kernel. It provides documentation
519 of which kernel options are used in a running kernel or in an
520 on-disk kernel. This information can be extracted from the kernel
521 image file with the script scripts/extract-ikconfig and used as
522 input to rebuild the current kernel or to build another kernel.
523 It can also be extracted from a running kernel by reading
524 /proc/config.gz if enabled (below).
527 bool "Enable access to .config through /proc/config.gz"
528 depends on IKCONFIG && PROC_FS
530 This option enables access to the kernel configuration file
531 through /proc/config.gz.
534 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
539 Select the minimal kernel log buffer size as a power of 2.
540 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
541 parameter, see below. Any higher size also might be forced
542 by "log_buf_len" boot parameter.
552 config LOG_CPU_MAX_BUF_SHIFT
553 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
556 default 12 if !BASE_SMALL
557 default 0 if BASE_SMALL
560 This option allows to increase the default ring buffer size
561 according to the number of CPUs. The value defines the contribution
562 of each CPU as a power of 2. The used space is typically only few
563 lines however it might be much more when problems are reported,
566 The increased size means that a new buffer has to be allocated and
567 the original static one is unused. It makes sense only on systems
568 with more CPUs. Therefore this value is used only when the sum of
569 contributions is greater than the half of the default kernel ring
570 buffer as defined by LOG_BUF_SHIFT. The default values are set
571 so that more than 64 CPUs are needed to trigger the allocation.
573 Also this option is ignored when "log_buf_len" kernel parameter is
574 used as it forces an exact (power of two) size of the ring buffer.
576 The number of possible CPUs is used for this computation ignoring
577 hotplugging making the computation optimal for the worst case
578 scenario while allowing a simple algorithm to be used from bootup.
580 Examples shift values and their meaning:
581 17 => 128 KB for each CPU
582 16 => 64 KB for each CPU
583 15 => 32 KB for each CPU
584 14 => 16 KB for each CPU
585 13 => 8 KB for each CPU
586 12 => 4 KB for each CPU
588 config PRINTK_SAFE_LOG_BUF_SHIFT
589 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
594 Select the size of an alternate printk per-CPU buffer where messages
595 printed from usafe contexts are temporary stored. One example would
596 be NMI messages, another one - printk recursion. The messages are
597 copied to the main log buffer in a safe context to avoid a deadlock.
598 The value defines the size as a power of 2.
600 Those messages are rare and limited. The largest one is when
601 a backtrace is printed. It usually fits into 4KB. Select
602 8KB if you want to be on the safe side.
605 17 => 128 KB for each CPU
606 16 => 64 KB for each CPU
607 15 => 32 KB for each CPU
608 14 => 16 KB for each CPU
609 13 => 8 KB for each CPU
610 12 => 4 KB for each CPU
613 # Architectures with an unreliable sched_clock() should select this:
615 config HAVE_UNSTABLE_SCHED_CLOCK
618 config GENERIC_SCHED_CLOCK
622 # For architectures that want to enable the support for NUMA-affine scheduler
625 config ARCH_SUPPORTS_NUMA_BALANCING
629 # For architectures that prefer to flush all TLBs after a number of pages
630 # are unmapped instead of sending one IPI per page to flush. The architecture
631 # must provide guarantees on what happens if a clean TLB cache entry is
632 # written after the unmap. Details are in mm/rmap.c near the check for
633 # should_defer_flush. The architecture should also consider if the full flush
634 # and the refill costs are offset by the savings of sending fewer IPIs.
635 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
639 # For architectures that know their GCC __int128 support is sound
641 config ARCH_SUPPORTS_INT128
644 # For architectures that (ab)use NUMA to represent different memory regions
645 # all cpu-local but of different latencies, such as SuperH.
647 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
650 config NUMA_BALANCING
651 bool "Memory placement aware NUMA scheduler"
652 depends on ARCH_SUPPORTS_NUMA_BALANCING
653 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
654 depends on SMP && NUMA && MIGRATION
656 This option adds support for automatic NUMA aware memory/task placement.
657 The mechanism is quite primitive and is based on migrating memory when
658 it has references to the node the task is running on.
660 This system will be inactive on UMA systems.
662 config NUMA_BALANCING_DEFAULT_ENABLED
663 bool "Automatically enable NUMA aware memory/task placement"
665 depends on NUMA_BALANCING
667 If set, automatic NUMA balancing will be enabled if running on a NUMA
671 bool "Control Group support"
674 This option adds support for grouping sets of processes together, for
675 use with process control subsystems such as Cpusets, CFS, memory
676 controls or device isolation.
678 - Documentation/scheduler/sched-design-CFS.txt (CFS)
679 - Documentation/cgroup-v1/ (features for grouping, isolation
680 and resource control)
690 bool "Memory controller"
694 Provides control over the memory footprint of tasks in a cgroup.
697 bool "Swap controller"
698 depends on MEMCG && SWAP
700 Provides control over the swap space consumed by tasks in a cgroup.
702 config MEMCG_SWAP_ENABLED
703 bool "Swap controller enabled by default"
704 depends on MEMCG_SWAP
707 Memory Resource Controller Swap Extension comes with its price in
708 a bigger memory consumption. General purpose distribution kernels
709 which want to enable the feature but keep it disabled by default
710 and let the user enable it by swapaccount=1 boot command line
711 parameter should have this option unselected.
712 For those who want to have the feature enabled by default should
713 select this option (if, for some reason, they need to disable it
714 then swapaccount=0 does the trick).
718 depends on MEMCG && !SLOB
726 Generic block IO controller cgroup interface. This is the common
727 cgroup interface which should be used by various IO controlling
730 Currently, CFQ IO scheduler uses it to recognize task groups and
731 control disk bandwidth allocation (proportional time slice allocation)
732 to such task groups. It is also used by bio throttling logic in
733 block layer to implement upper limit in IO rates on a device.
735 This option only enables generic Block IO controller infrastructure.
736 One needs to also enable actual IO controlling logic/policy. For
737 enabling proportional weight division of disk bandwidth in CFQ, set
738 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
739 CONFIG_BLK_DEV_THROTTLING=y.
741 See Documentation/cgroup-v1/blkio-controller.txt for more information.
743 config DEBUG_BLK_CGROUP
744 bool "IO controller debugging"
745 depends on BLK_CGROUP
748 Enable some debugging help. Currently it exports additional stat
749 files in a cgroup which can be useful for debugging.
751 config CGROUP_WRITEBACK
753 depends on MEMCG && BLK_CGROUP
756 menuconfig CGROUP_SCHED
757 bool "CPU controller"
760 This feature lets CPU scheduler recognize task groups and control CPU
761 bandwidth allocation to such task groups. It uses cgroups to group
765 config FAIR_GROUP_SCHED
766 bool "Group scheduling for SCHED_OTHER"
767 depends on CGROUP_SCHED
771 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
772 depends on FAIR_GROUP_SCHED
775 This option allows users to define CPU bandwidth rates (limits) for
776 tasks running within the fair group scheduler. Groups with no limit
777 set are considered to be unconstrained and will run with no
779 See Documentation/scheduler/sched-bwc.txt for more information.
781 config RT_GROUP_SCHED
782 bool "Group scheduling for SCHED_RR/FIFO"
783 depends on CGROUP_SCHED
786 This feature lets you explicitly allocate real CPU bandwidth
787 to task groups. If enabled, it will also make it impossible to
788 schedule realtime tasks for non-root users until you allocate
789 realtime bandwidth for them.
790 See Documentation/scheduler/sched-rt-group.txt for more information.
795 bool "PIDs controller"
797 Provides enforcement of process number limits in the scope of a
798 cgroup. Any attempt to fork more processes than is allowed in the
799 cgroup will fail. PIDs are fundamentally a global resource because it
800 is fairly trivial to reach PID exhaustion before you reach even a
801 conservative kmemcg limit. As a result, it is possible to grind a
802 system to halt without being limited by other cgroup policies. The
803 PIDs controller is designed to stop this from happening.
805 It should be noted that organisational operations (such as attaching
806 to a cgroup hierarchy will *not* be blocked by the PIDs controller),
807 since the PIDs limit only affects a process's ability to fork, not to
811 bool "RDMA controller"
813 Provides enforcement of RDMA resources defined by IB stack.
814 It is fairly easy for consumers to exhaust RDMA resources, which
815 can result into resource unavailability to other consumers.
816 RDMA controller is designed to stop this from happening.
817 Attaching processes with active RDMA resources to the cgroup
818 hierarchy is allowed even if can cross the hierarchy's limit.
820 config CGROUP_FREEZER
821 bool "Freezer controller"
823 Provides a way to freeze and unfreeze all tasks in a
826 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
827 controller includes important in-kernel memory consumers per default.
829 If you're using cgroup2, say N.
831 config CGROUP_HUGETLB
832 bool "HugeTLB controller"
833 depends on HUGETLB_PAGE
837 Provides a cgroup controller for HugeTLB pages.
838 When you enable this, you can put a per cgroup limit on HugeTLB usage.
839 The limit is enforced during page fault. Since HugeTLB doesn't
840 support page reclaim, enforcing the limit at page fault time implies
841 that, the application will get SIGBUS signal if it tries to access
842 HugeTLB pages beyond its limit. This requires the application to know
843 beforehand how much HugeTLB pages it would require for its use. The
844 control group is tracked in the third page lru pointer. This means
845 that we cannot use the controller with huge page less than 3 pages.
848 bool "Cpuset controller"
851 This option will let you create and manage CPUSETs which
852 allow dynamically partitioning a system into sets of CPUs and
853 Memory Nodes and assigning tasks to run only within those sets.
854 This is primarily useful on large SMP or NUMA systems.
858 config PROC_PID_CPUSET
859 bool "Include legacy /proc/<pid>/cpuset file"
864 bool "Device controller"
866 Provides a cgroup controller implementing whitelists for
867 devices which a process in the cgroup can mknod or open.
869 config CGROUP_CPUACCT
870 bool "Simple CPU accounting controller"
872 Provides a simple controller for monitoring the
873 total CPU consumed by the tasks in a cgroup.
876 bool "Perf controller"
877 depends on PERF_EVENTS
879 This option extends the perf per-cpu mode to restrict monitoring
880 to threads which belong to the cgroup specified and run on the
886 bool "Support for eBPF programs attached to cgroups"
887 depends on BPF_SYSCALL
888 select SOCK_CGROUP_DATA
890 Allow attaching eBPF programs to a cgroup using the bpf(2)
891 syscall command BPF_PROG_ATTACH.
893 In which context these programs are accessed depends on the type
894 of attachment. For instance, programs that are attached using
895 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
899 bool "Debug controller"
901 depends on DEBUG_KERNEL
903 This option enables a simple controller that exports
904 debugging information about the cgroups framework. This
905 controller is for control cgroup debugging only. Its
906 interfaces are not stable.
910 config SOCK_CGROUP_DATA
916 menuconfig NAMESPACES
917 bool "Namespaces support" if EXPERT
921 Provides the way to make tasks work with different objects using
922 the same id. For example same IPC id may refer to different objects
923 or same user id or pid may refer to different tasks when used in
924 different namespaces.
932 In this namespace tasks see different info provided with the
937 depends on (SYSVIPC || POSIX_MQUEUE)
940 In this namespace tasks work with IPC ids which correspond to
941 different IPC objects in different namespaces.
944 bool "User namespace"
947 This allows containers, i.e. vservers, to use user namespaces
948 to provide different user info for different servers.
950 When user namespaces are enabled in the kernel it is
951 recommended that the MEMCG option also be enabled and that
952 user-space use the memory control groups to limit the amount
953 of memory a memory unprivileged users can use.
958 bool "PID Namespaces"
961 Support process id namespaces. This allows having multiple
962 processes with the same pid as long as they are in different
963 pid namespaces. This is a building block of containers.
966 bool "Network namespace"
970 Allow user space to create what appear to be multiple instances
971 of the network stack.
975 config CHECKPOINT_RESTORE
976 bool "Checkpoint/restore support"
980 Enables additional kernel features in a sake of checkpoint/restore.
981 In particular it adds auxiliary prctl codes to setup process text,
982 data and heap segment sizes, and a few additional /proc filesystem
985 If unsure, say N here.
987 config SCHED_AUTOGROUP
988 bool "Automatic process group scheduling"
991 select FAIR_GROUP_SCHED
993 This option optimizes the scheduler for common desktop workloads by
994 automatically creating and populating task groups. This separation
995 of workloads isolates aggressive CPU burners (like build jobs) from
996 desktop applications. Task group autogeneration is currently based
999 config SYSFS_DEPRECATED
1000 bool "Enable deprecated sysfs features to support old userspace tools"
1004 This option adds code that switches the layout of the "block" class
1005 devices, to not show up in /sys/class/block/, but only in
1008 This switch is only active when the sysfs.deprecated=1 boot option is
1009 passed or the SYSFS_DEPRECATED_V2 option is set.
1011 This option allows new kernels to run on old distributions and tools,
1012 which might get confused by /sys/class/block/. Since 2007/2008 all
1013 major distributions and tools handle this just fine.
1015 Recent distributions and userspace tools after 2009/2010 depend on
1016 the existence of /sys/class/block/, and will not work with this
1019 Only if you are using a new kernel on an old distribution, you might
1022 config SYSFS_DEPRECATED_V2
1023 bool "Enable deprecated sysfs features by default"
1026 depends on SYSFS_DEPRECATED
1028 Enable deprecated sysfs by default.
1030 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1033 Only if you are using a new kernel on an old distribution, you might
1034 need to say Y here. Even then, odds are you would not need it
1035 enabled, you can always pass the boot option if absolutely necessary.
1038 bool "Kernel->user space relay support (formerly relayfs)"
1041 This option enables support for relay interface support in
1042 certain file systems (such as debugfs).
1043 It is designed to provide an efficient mechanism for tools and
1044 facilities to relay large amounts of data from kernel space to
1049 config BLK_DEV_INITRD
1050 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1052 The initial RAM filesystem is a ramfs which is loaded by the
1053 boot loader (loadlin or lilo) and that is mounted as root
1054 before the normal boot procedure. It is typically used to
1055 load modules needed to mount the "real" root file system,
1056 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1058 If RAM disk support (BLK_DEV_RAM) is also included, this
1059 also enables initial RAM disk (initrd) support and adds
1060 15 Kbytes (more on some other architectures) to the kernel size.
1066 source "usr/Kconfig"
1071 prompt "Compiler optimization level"
1072 default CC_OPTIMIZE_FOR_PERFORMANCE
1074 config CC_OPTIMIZE_FOR_PERFORMANCE
1075 bool "Optimize for performance"
1077 This is the default optimization level for the kernel, building
1078 with the "-O2" compiler flag for best performance and most
1079 helpful compile-time warnings.
1081 config CC_OPTIMIZE_FOR_SIZE
1082 bool "Optimize for size"
1084 Enabling this option will pass "-Os" instead of "-O2" to
1085 your compiler resulting in a smaller kernel.
1091 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1094 This requires that the arch annotates or otherwise protects
1095 its external entry points from being discarded. Linker scripts
1096 must also merge .text.*, .data.*, and .bss.* correctly into
1097 output sections. Care must be taken not to pull in unrelated
1098 sections (e.g., '.text.init'). Typically '.' in section names
1099 is used to distinguish them from label names / C identifiers.
1101 config LD_DEAD_CODE_DATA_ELIMINATION
1102 bool "Dead code and data elimination (EXPERIMENTAL)"
1103 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1105 depends on $(cc-option,-ffunction-sections -fdata-sections)
1106 depends on $(ld-option,--gc-sections)
1108 Enable this if you want to do dead code and data elimination with
1109 the linker by compiling with -ffunction-sections -fdata-sections,
1110 and linking with --gc-sections.
1112 This can reduce on disk and in-memory size of the kernel
1113 code and static data, particularly for small configs and
1114 on small systems. This has the possibility of introducing
1115 silently broken kernel if the required annotations are not
1116 present. This option is not well tested yet, so use at your
1128 config SYSCTL_EXCEPTION_TRACE
1131 Enable support for /proc/sys/debug/exception-trace.
1133 config SYSCTL_ARCH_UNALIGN_NO_WARN
1136 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1137 Allows arch to define/use @no_unaligned_warning to possibly warn
1138 about unaligned access emulation going on under the hood.
1140 config SYSCTL_ARCH_UNALIGN_ALLOW
1143 Enable support for /proc/sys/kernel/unaligned-trap
1144 Allows arches to define/use @unaligned_enabled to runtime toggle
1145 the unaligned access emulation.
1146 see arch/parisc/kernel/unaligned.c for reference
1148 config HAVE_PCSPKR_PLATFORM
1151 # interpreter that classic socket filters depend on
1156 bool "Configure standard kernel features (expert users)"
1157 # Unhide debug options, to make the on-by-default options visible
1160 This option allows certain base kernel options and settings
1161 to be disabled or tweaked. This is for specialized
1162 environments which can tolerate a "non-standard" kernel.
1163 Only use this if you really know what you are doing.
1166 bool "Enable 16-bit UID system calls" if EXPERT
1167 depends on HAVE_UID16 && MULTIUSER
1170 This enables the legacy 16-bit UID syscall wrappers.
1173 bool "Multiple users, groups and capabilities support" if EXPERT
1176 This option enables support for non-root users, groups and
1179 If you say N here, all processes will run with UID 0, GID 0, and all
1180 possible capabilities. Saying N here also compiles out support for
1181 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1184 If unsure, say Y here.
1186 config SGETMASK_SYSCALL
1187 bool "sgetmask/ssetmask syscalls support" if EXPERT
1188 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1190 sys_sgetmask and sys_ssetmask are obsolete system calls
1191 no longer supported in libc but still enabled by default in some
1194 If unsure, leave the default option here.
1196 config SYSFS_SYSCALL
1197 bool "Sysfs syscall support" if EXPERT
1200 sys_sysfs is an obsolete system call no longer supported in libc.
1201 Note that disabling this option is more secure but might break
1202 compatibility with some systems.
1204 If unsure say Y here.
1206 config SYSCTL_SYSCALL
1207 bool "Sysctl syscall support" if EXPERT
1208 depends on PROC_SYSCTL
1212 sys_sysctl uses binary paths that have been found challenging
1213 to properly maintain and use. The interface in /proc/sys
1214 using paths with ascii names is now the primary path to this
1217 Almost nothing using the binary sysctl interface so if you are
1218 trying to save some space it is probably safe to disable this,
1219 making your kernel marginally smaller.
1221 If unsure say N here.
1224 bool "open by fhandle syscalls" if EXPERT
1228 If you say Y here, a user level program will be able to map
1229 file names to handle and then later use the handle for
1230 different file system operations. This is useful in implementing
1231 userspace file servers, which now track files using handles instead
1232 of names. The handle would remain the same even if file names
1233 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1237 bool "Posix Clocks & timers" if EXPERT
1240 This includes native support for POSIX timers to the kernel.
1241 Some embedded systems have no use for them and therefore they
1242 can be configured out to reduce the size of the kernel image.
1244 When this option is disabled, the following syscalls won't be
1245 available: timer_create, timer_gettime: timer_getoverrun,
1246 timer_settime, timer_delete, clock_adjtime, getitimer,
1247 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1248 clock_getres and clock_nanosleep syscalls will be limited to
1249 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1255 bool "Enable support for printk" if EXPERT
1258 This option enables normal printk support. Removing it
1259 eliminates most of the message strings from the kernel image
1260 and makes the kernel more or less silent. As this makes it
1261 very difficult to diagnose system problems, saying N here is
1262 strongly discouraged.
1270 bool "BUG() support" if EXPERT
1273 Disabling this option eliminates support for BUG and WARN, reducing
1274 the size of your kernel image and potentially quietly ignoring
1275 numerous fatal conditions. You should only consider disabling this
1276 option for embedded systems with no facilities for reporting errors.
1282 bool "Enable ELF core dumps" if EXPERT
1284 Enable support for generating core dumps. Disabling saves about 4k.
1287 config PCSPKR_PLATFORM
1288 bool "Enable PC-Speaker support" if EXPERT
1289 depends on HAVE_PCSPKR_PLATFORM
1293 This option allows to disable the internal PC-Speaker
1294 support, saving some memory.
1298 bool "Enable full-sized data structures for core" if EXPERT
1300 Disabling this option reduces the size of miscellaneous core
1301 kernel data structures. This saves memory on small machines,
1302 but may reduce performance.
1305 bool "Enable futex support" if EXPERT
1309 Disabling this option will cause the kernel to be built without
1310 support for "fast userspace mutexes". The resulting kernel may not
1311 run glibc-based applications correctly.
1315 depends on FUTEX && RT_MUTEXES
1318 config HAVE_FUTEX_CMPXCHG
1322 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1323 is implemented and always working. This removes a couple of runtime
1327 bool "Enable eventpoll support" if EXPERT
1331 Disabling this option will cause the kernel to be built without
1332 support for epoll family of system calls.
1335 bool "Enable signalfd() system call" if EXPERT
1339 Enable the signalfd() system call that allows to receive signals
1340 on a file descriptor.
1345 bool "Enable timerfd() system call" if EXPERT
1349 Enable the timerfd() system call that allows to receive timer
1350 events on a file descriptor.
1355 bool "Enable eventfd() system call" if EXPERT
1359 Enable the eventfd() system call that allows to receive both
1360 kernel notification (ie. KAIO) or userspace notifications.
1365 bool "Use full shmem filesystem" if EXPERT
1369 The shmem is an internal filesystem used to manage shared memory.
1370 It is backed by swap and manages resource limits. It is also exported
1371 to userspace as tmpfs if TMPFS is enabled. Disabling this
1372 option replaces shmem and tmpfs with the much simpler ramfs code,
1373 which may be appropriate on small systems without swap.
1376 bool "Enable AIO support" if EXPERT
1379 This option enables POSIX asynchronous I/O which may by used
1380 by some high performance threaded applications. Disabling
1381 this option saves about 7k.
1383 config ADVISE_SYSCALLS
1384 bool "Enable madvise/fadvise syscalls" if EXPERT
1387 This option enables the madvise and fadvise syscalls, used by
1388 applications to advise the kernel about their future memory or file
1389 usage, improving performance. If building an embedded system where no
1390 applications use these syscalls, you can disable this option to save
1394 bool "Enable membarrier() system call" if EXPERT
1397 Enable the membarrier() system call that allows issuing memory
1398 barriers across all running threads, which can be used to distribute
1399 the cost of user-space memory barriers asymmetrically by transforming
1400 pairs of memory barriers into pairs consisting of membarrier() and a
1406 bool "Load all symbols for debugging/ksymoops" if EXPERT
1409 Say Y here to let the kernel print out symbolic crash information and
1410 symbolic stack backtraces. This increases the size of the kernel
1411 somewhat, as all symbols have to be loaded into the kernel image.
1414 bool "Include all symbols in kallsyms"
1415 depends on DEBUG_KERNEL && KALLSYMS
1417 Normally kallsyms only contains the symbols of functions for nicer
1418 OOPS messages and backtraces (i.e., symbols from the text and inittext
1419 sections). This is sufficient for most cases. And only in very rare
1420 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1421 names of variables from the data sections, etc).
1423 This option makes sure that all symbols are loaded into the kernel
1424 image (i.e., symbols from all sections) in cost of increased kernel
1425 size (depending on the kernel configuration, it may be 300KiB or
1426 something like this).
1428 Say N unless you really need all symbols.
1430 config KALLSYMS_ABSOLUTE_PERCPU
1433 default X86_64 && SMP
1435 config KALLSYMS_BASE_RELATIVE
1440 Instead of emitting them as absolute values in the native word size,
1441 emit the symbol references in the kallsyms table as 32-bit entries,
1442 each containing a relative value in the range [base, base + U32_MAX]
1443 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1444 an absolute value in the range [0, S32_MAX] or a relative value in the
1445 range [base, base + S32_MAX], where base is the lowest relative symbol
1446 address encountered in the image.
1448 On 64-bit builds, this reduces the size of the address table by 50%,
1449 but more importantly, it results in entries whose values are build
1450 time constants, and no relocation pass is required at runtime to fix
1451 up the entries based on the runtime load address of the kernel.
1453 # end of the "standard kernel features (expert users)" menu
1455 # syscall, maps, verifier
1457 bool "Enable bpf() system call"
1463 Enable the bpf() system call that allows to manipulate eBPF
1464 programs and maps via file descriptors.
1466 config BPF_JIT_ALWAYS_ON
1467 bool "Permanently enable BPF JIT and remove BPF interpreter"
1468 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1470 Enables BPF JIT and removes BPF interpreter to avoid
1471 speculative execution of BPF instructions by the interpreter
1474 bool "Enable userfaultfd() system call"
1478 Enable the userfaultfd() system call that allows to intercept and
1479 handle page faults in userland.
1481 config ARCH_HAS_MEMBARRIER_CALLBACKS
1484 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1488 bool "Enable rseq() system call" if EXPERT
1490 depends on HAVE_RSEQ
1493 Enable the restartable sequences system call. It provides a
1494 user-space cache for the current CPU number value, which
1495 speeds up getting the current CPU number from user-space,
1496 as well as an ABI to speed up user-space operations on
1503 bool "Enabled debugging of rseq() system call" if EXPERT
1504 depends on RSEQ && DEBUG_KERNEL
1506 Enable extra debugging checks for the rseq system call.
1511 bool "Embedded system"
1512 option allnoconfig_y
1515 This option should be enabled if compiling the kernel for
1516 an embedded system so certain expert options are available
1519 config HAVE_PERF_EVENTS
1522 See tools/perf/design.txt for details.
1524 config PERF_USE_VMALLOC
1527 See tools/perf/design.txt for details
1530 bool "PC/104 support" if EXPERT
1532 Expose PC/104 form factor device drivers and options available for
1533 selection and configuration. Enable this option if your target
1534 machine has a PC/104 bus.
1536 menu "Kernel Performance Events And Counters"
1539 bool "Kernel performance events and counters"
1540 default y if PROFILING
1541 depends on HAVE_PERF_EVENTS
1546 Enable kernel support for various performance events provided
1547 by software and hardware.
1549 Software events are supported either built-in or via the
1550 use of generic tracepoints.
1552 Most modern CPUs support performance events via performance
1553 counter registers. These registers count the number of certain
1554 types of hw events: such as instructions executed, cachemisses
1555 suffered, or branches mis-predicted - without slowing down the
1556 kernel or applications. These registers can also trigger interrupts
1557 when a threshold number of events have passed - and can thus be
1558 used to profile the code that runs on that CPU.
1560 The Linux Performance Event subsystem provides an abstraction of
1561 these software and hardware event capabilities, available via a
1562 system call and used by the "perf" utility in tools/perf/. It
1563 provides per task and per CPU counters, and it provides event
1564 capabilities on top of those.
1568 config DEBUG_PERF_USE_VMALLOC
1570 bool "Debug: use vmalloc to back perf mmap() buffers"
1571 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1572 select PERF_USE_VMALLOC
1574 Use vmalloc memory to back perf mmap() buffers.
1576 Mostly useful for debugging the vmalloc code on platforms
1577 that don't require it.
1583 config VM_EVENT_COUNTERS
1585 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1587 VM event counters are needed for event counts to be shown.
1588 This option allows the disabling of the VM event counters
1589 on EXPERT systems. /proc/vmstat will only show page counts
1590 if VM event counters are disabled.
1594 bool "Enable SLUB debugging support" if EXPERT
1595 depends on SLUB && SYSFS
1597 SLUB has extensive debug support features. Disabling these can
1598 result in significant savings in code size. This also disables
1599 SLUB sysfs support. /sys/slab will not exist and there will be
1600 no support for cache validation etc.
1602 config SLUB_MEMCG_SYSFS_ON
1604 bool "Enable memcg SLUB sysfs support by default" if EXPERT
1605 depends on SLUB && SYSFS && MEMCG
1607 SLUB creates a directory under /sys/kernel/slab for each
1608 allocation cache to host info and debug files. If memory
1609 cgroup is enabled, each cache can have per memory cgroup
1610 caches. SLUB can create the same sysfs directories for these
1611 caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1612 to a very high number of debug files being created. This is
1613 controlled by slub_memcg_sysfs boot parameter and this
1614 config option determines the parameter's default value.
1617 bool "Disable heap randomization"
1620 Randomizing heap placement makes heap exploits harder, but it
1621 also breaks ancient binaries (including anything libc5 based).
1622 This option changes the bootup default to heap randomization
1623 disabled, and can be overridden at runtime by setting
1624 /proc/sys/kernel/randomize_va_space to 2.
1626 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1629 prompt "Choose SLAB allocator"
1632 This option allows to select a slab allocator.
1636 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1638 The regular slab allocator that is established and known to work
1639 well in all environments. It organizes cache hot objects in
1640 per cpu and per node queues.
1643 bool "SLUB (Unqueued Allocator)"
1644 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1646 SLUB is a slab allocator that minimizes cache line usage
1647 instead of managing queues of cached objects (SLAB approach).
1648 Per cpu caching is realized using slabs of objects instead
1649 of queues of objects. SLUB can use memory efficiently
1650 and has enhanced diagnostics. SLUB is the default choice for
1655 bool "SLOB (Simple Allocator)"
1657 SLOB replaces the stock allocator with a drastically simpler
1658 allocator. SLOB is generally more space efficient but
1659 does not perform as well on large systems.
1663 config SLAB_MERGE_DEFAULT
1664 bool "Allow slab caches to be merged"
1667 For reduced kernel memory fragmentation, slab caches can be
1668 merged when they share the same size and other characteristics.
1669 This carries a risk of kernel heap overflows being able to
1670 overwrite objects from merged caches (and more easily control
1671 cache layout), which makes such heap attacks easier to exploit
1672 by attackers. By keeping caches unmerged, these kinds of exploits
1673 can usually only damage objects in the same cache. To disable
1674 merging at runtime, "slab_nomerge" can be passed on the kernel
1677 config SLAB_FREELIST_RANDOM
1679 depends on SLAB || SLUB
1680 bool "SLAB freelist randomization"
1682 Randomizes the freelist order used on creating new pages. This
1683 security feature reduces the predictability of the kernel slab
1684 allocator against heap overflows.
1686 config SLAB_FREELIST_HARDENED
1687 bool "Harden slab freelist metadata"
1690 Many kernel heap attacks try to target slab cache metadata and
1691 other infrastructure. This options makes minor performance
1692 sacrifies to harden the kernel slab allocator against common
1693 freelist exploit methods.
1695 config SLUB_CPU_PARTIAL
1697 depends on SLUB && SMP
1698 bool "SLUB per cpu partial cache"
1700 Per cpu partial caches accellerate objects allocation and freeing
1701 that is local to a processor at the price of more indeterminism
1702 in the latency of the free. On overflow these caches will be cleared
1703 which requires the taking of locks that may cause latency spikes.
1704 Typically one would choose no for a realtime system.
1706 config MMAP_ALLOW_UNINITIALIZED
1707 bool "Allow mmapped anonymous memory to be uninitialized"
1708 depends on EXPERT && !MMU
1711 Normally, and according to the Linux spec, anonymous memory obtained
1712 from mmap() has its contents cleared before it is passed to
1713 userspace. Enabling this config option allows you to request that
1714 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1715 providing a huge performance boost. If this option is not enabled,
1716 then the flag will be ignored.
1718 This is taken advantage of by uClibc's malloc(), and also by
1719 ELF-FDPIC binfmt's brk and stack allocator.
1721 Because of the obvious security issues, this option should only be
1722 enabled on embedded devices where you control what is run in
1723 userspace. Since that isn't generally a problem on no-MMU systems,
1724 it is normally safe to say Y here.
1726 See Documentation/nommu-mmap.txt for more information.
1728 config SYSTEM_DATA_VERIFICATION
1730 select SYSTEM_TRUSTED_KEYRING
1734 select ASYMMETRIC_KEY_TYPE
1735 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1738 select X509_CERTIFICATE_PARSER
1739 select PKCS7_MESSAGE_PARSER
1741 Provide PKCS#7 message verification using the contents of the system
1742 trusted keyring to provide public keys. This then can be used for
1743 module verification, kexec image verification and firmware blob
1747 bool "Profiling support"
1749 Say Y here to enable the extended profiling support mechanisms used
1750 by profilers such as OProfile.
1753 # Place an empty function call at each tracepoint site. Can be
1754 # dynamically changed for a probe function.
1759 endmenu # General setup
1761 source "arch/Kconfig"
1768 default 0 if BASE_FULL
1769 default 1 if !BASE_FULL
1772 bool "Enable loadable module support"
1775 Kernel modules are small pieces of compiled code which can
1776 be inserted in the running kernel, rather than being
1777 permanently built into the kernel. You use the "modprobe"
1778 tool to add (and sometimes remove) them. If you say Y here,
1779 many parts of the kernel can be built as modules (by
1780 answering M instead of Y where indicated): this is most
1781 useful for infrequently used options which are not required
1782 for booting. For more information, see the man pages for
1783 modprobe, lsmod, modinfo, insmod and rmmod.
1785 If you say Y here, you will need to run "make
1786 modules_install" to put the modules under /lib/modules/
1787 where modprobe can find them (you may need to be root to do
1794 config MODULE_FORCE_LOAD
1795 bool "Forced module loading"
1798 Allow loading of modules without version information (ie. modprobe
1799 --force). Forced module loading sets the 'F' (forced) taint flag and
1800 is usually a really bad idea.
1802 config MODULE_UNLOAD
1803 bool "Module unloading"
1805 Without this option you will not be able to unload any
1806 modules (note that some modules may not be unloadable
1807 anyway), which makes your kernel smaller, faster
1808 and simpler. If unsure, say Y.
1810 config MODULE_FORCE_UNLOAD
1811 bool "Forced module unloading"
1812 depends on MODULE_UNLOAD
1814 This option allows you to force a module to unload, even if the
1815 kernel believes it is unsafe: the kernel will remove the module
1816 without waiting for anyone to stop using it (using the -f option to
1817 rmmod). This is mainly for kernel developers and desperate users.
1821 bool "Module versioning support"
1823 Usually, you have to use modules compiled with your kernel.
1824 Saying Y here makes it sometimes possible to use modules
1825 compiled for different kernels, by adding enough information
1826 to the modules to (hopefully) spot any changes which would
1827 make them incompatible with the kernel you are running. If
1830 config MODULE_REL_CRCS
1832 depends on MODVERSIONS
1834 config MODULE_SRCVERSION_ALL
1835 bool "Source checksum for all modules"
1837 Modules which contain a MODULE_VERSION get an extra "srcversion"
1838 field inserted into their modinfo section, which contains a
1839 sum of the source files which made it. This helps maintainers
1840 see exactly which source was used to build a module (since
1841 others sometimes change the module source without updating
1842 the version). With this option, such a "srcversion" field
1843 will be created for all modules. If unsure, say N.
1846 bool "Module signature verification"
1848 select SYSTEM_DATA_VERIFICATION
1850 Check modules for valid signatures upon load: the signature
1851 is simply appended to the module. For more information see
1852 <file:Documentation/admin-guide/module-signing.rst>.
1854 Note that this option adds the OpenSSL development packages as a
1855 kernel build dependency so that the signing tool can use its crypto
1858 !!!WARNING!!! If you enable this option, you MUST make sure that the
1859 module DOES NOT get stripped after being signed. This includes the
1860 debuginfo strip done by some packagers (such as rpmbuild) and
1861 inclusion into an initramfs that wants the module size reduced.
1863 config MODULE_SIG_FORCE
1864 bool "Require modules to be validly signed"
1865 depends on MODULE_SIG
1867 Reject unsigned modules or signed modules for which we don't have a
1868 key. Without this, such modules will simply taint the kernel.
1870 config MODULE_SIG_ALL
1871 bool "Automatically sign all modules"
1873 depends on MODULE_SIG
1875 Sign all modules during make modules_install. Without this option,
1876 modules must be signed manually, using the scripts/sign-file tool.
1878 comment "Do not forget to sign required modules with scripts/sign-file"
1879 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1882 prompt "Which hash algorithm should modules be signed with?"
1883 depends on MODULE_SIG
1885 This determines which sort of hashing algorithm will be used during
1886 signature generation. This algorithm _must_ be built into the kernel
1887 directly so that signature verification can take place. It is not
1888 possible to load a signed module containing the algorithm to check
1889 the signature on that module.
1891 config MODULE_SIG_SHA1
1892 bool "Sign modules with SHA-1"
1895 config MODULE_SIG_SHA224
1896 bool "Sign modules with SHA-224"
1897 select CRYPTO_SHA256
1899 config MODULE_SIG_SHA256
1900 bool "Sign modules with SHA-256"
1901 select CRYPTO_SHA256
1903 config MODULE_SIG_SHA384
1904 bool "Sign modules with SHA-384"
1905 select CRYPTO_SHA512
1907 config MODULE_SIG_SHA512
1908 bool "Sign modules with SHA-512"
1909 select CRYPTO_SHA512
1913 config MODULE_SIG_HASH
1915 depends on MODULE_SIG
1916 default "sha1" if MODULE_SIG_SHA1
1917 default "sha224" if MODULE_SIG_SHA224
1918 default "sha256" if MODULE_SIG_SHA256
1919 default "sha384" if MODULE_SIG_SHA384
1920 default "sha512" if MODULE_SIG_SHA512
1922 config MODULE_COMPRESS
1923 bool "Compress modules on installation"
1927 Compresses kernel modules when 'make modules_install' is run; gzip or
1928 xz depending on "Compression algorithm" below.
1930 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
1932 Out-of-tree kernel modules installed using Kbuild will also be
1933 compressed upon installation.
1935 Note: for modules inside an initrd or initramfs, it's more efficient
1936 to compress the whole initrd or initramfs instead.
1938 Note: This is fully compatible with signed modules.
1943 prompt "Compression algorithm"
1944 depends on MODULE_COMPRESS
1945 default MODULE_COMPRESS_GZIP
1947 This determines which sort of compression will be used during
1948 'make modules_install'.
1950 GZIP (default) and XZ are supported.
1952 config MODULE_COMPRESS_GZIP
1955 config MODULE_COMPRESS_XZ
1960 config TRIM_UNUSED_KSYMS
1961 bool "Trim unused exported kernel symbols"
1962 depends on MODULES && !UNUSED_SYMBOLS
1964 The kernel and some modules make many symbols available for
1965 other modules to use via EXPORT_SYMBOL() and variants. Depending
1966 on the set of modules being selected in your kernel configuration,
1967 many of those exported symbols might never be used.
1969 This option allows for unused exported symbols to be dropped from
1970 the build. In turn, this provides the compiler more opportunities
1971 (especially when using LTO) for optimizing the code and reducing
1972 binary size. This might have some security advantages as well.
1974 If unsure, or if you need to build out-of-tree modules, say N.
1978 config MODULES_TREE_LOOKUP
1980 depends on PERF_EVENTS || TRACING
1982 config INIT_ALL_POSSIBLE
1985 Back when each arch used to define their own cpu_online_mask and
1986 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1987 with all 1s, and others with all 0s. When they were centralised,
1988 it was better to provide this option than to break all the archs
1989 and have several arch maintainers pursuing me down dark alleys.
1991 source "block/Kconfig"
1993 config PREEMPT_NOTIFIERS
2003 Build a simple ASN.1 grammar compiler that produces a bytecode output
2004 that can be interpreted by the ASN.1 stream decoder and used to
2005 inform it as to what tags are to be expected in a stream and what
2006 functions to call on what tags.
2008 source "kernel/Kconfig.locks"
2010 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2013 # It may be useful for an architecture to override the definitions of the
2014 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2015 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2016 # different calling convention for syscalls. They can also override the
2017 # macros for not-implemented syscalls in kernel/sys_ni.c and
2018 # kernel/time/posix-stubs.c. All these overrides need to be available in
2019 # <asm/syscall_wrapper.h>.
2020 config ARCH_HAS_SYSCALL_WRAPPER
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